Charged block co-polymers as pour point depressants

ABSTRACT

Fouling components within a fluid may be prevented from accumulating when an additive contacts the fluid, e.g. by coating the wellbore with the additive prior to the production of the fluid or adding the additive directly to the fluid, etc.. The additive may include, but is not limited to, a block copolymer having at least two components. The first component may be a charged monomer, and the second component may be a long chain fatty alcohol acrylate monomer. In one alternative embodiment, the fluid may be an oil-based fluid produced through a wellbore or an oil-based wellbore fluid, and the fouling components may be or include, but are not limited to, wax, paraffins, asphaltene, resins, and combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application and claims priority toU.S. application Ser. No. 13/919,671 filed Jun. 17, 2013, which claimsthe benefit of U.S. Provisional Patent Application No. 61/663,178 filedJun. 22, 2012, both of which are incorporated by reference herein intheir entirety

TECHNICAL FIELD

The present invention relates to at least partially reducing anaccumulation of at least one fouling component within a fluid by addingan additive to the fluid, and more particularly relates in onenon-limiting embodiment to preventing waxes, paraffins, and combinationsthereof within the fluid from agglomerating or precipitating within thefluid.

BACKGROUND

Fuel oils, crude oils, refinery fluids, lubricants and/or petroleumproducts may often contain fouling components, e.g., paraffins, waxes,etc. that may agglomerate or precipitate, particularly at lowtemperatures, as large crystals in such a way that may cause the oil tolose its ability to flow, i.e. the pour point becomes higher because ofthe fouling components within the fluid. The ‘pour point’ of a fluid isthe temperature at which a fluid ceases to pour. One test to determinethe pour point is the ASTM D-97 pour point test where the oil ceases toflow at a given temperature (the pour point) when the sample is held at90 degrees to the upright for five seconds. Higher pour points aretypically associated with crude oils having significant paraffin or waxcontent because these fouling components begin precipitating as thetemperature of the fluid decreases. At some point, the precipitates mayaccumulate and/or agglomerate to the point where the fluid will nolonger flow. ‘Fouling component’ is defined herein to be any componentthat may agglomerate or precipitate in a fluid.

As the temperature of the fluid falls and approaches the pour point,difficulties arise in transporting the fuel or lubricant through linesand pumps. Further, the wax crystals tend to plug fuel lines, screens,and filters at temperatures above the pour point. These problems arewell recognized in the art, and various additives have been proposed,many of which are in commercial use, for depressing the pour point offuel oils and lubricants. Similarly, other additives have been proposedand are in commercial use for reducing the size and changing the shapeof the wax crystals that do form. Smaller size crystals are desirablesince they are less likely to clog a filter, but these smaller crystalsmay still agglomerate and form larger crystals and subsequently pose thesame problem of plugging or clogging various types of well equipment.Thus, it would be beneficial to also prevent the smaller crystals fromagglomerating and/or precipitating, or otherwise accumulating.

Such well treatment agents may be placed in contact with the oilfieldfluids contained in the formation before such fluids enter the wellborewhere deleterious effects are commonly encountered. Various welltreatment agents are often used in production wells to prevent thedeleterious effects caused by such formations and precipitates. Forinstance, pour point depressants and wax crystal modifiers have beenused to change the nature of wax crystals that precipitate from thepetroleum fuel, lubricant or crude oil, thereby reducing the tendency ofwax crystals to plug equipment

It would be desirable if the aforementioned fluid compositions andmethods for using such fluids could be tailored to prevent theagglomerating and/or precipitating of these types of fouling componentswithin the fluid, and thereby reduce the pour point of the fluid.

SUMMARY

There is provided, in one form, a method for contacting a fluid havingwax, paraffins, and/or asphaltene that is a crude oil, a refinery fluid,a lubricant, and/or a fuel oil with an additive in an effective amountfor at least partially reducing an accumulation of the foulingcomponent(s). The additive may include, but is not limited to a blockcopolymer having at least two components. The first component may be acharged monomer, and the second component may be a long chain fattyalcohol acrylate monomer. The first component may be or include, but isnot limited to a cationic acrylate based monomer, a salt of acrylicacid, a salt of methacrylic acid, a salt of carboxyethyl acrylate, asalt of carboxyethyl methacrylate, a sulfonated styrene, a cationicstyrene derivative, an ester derived from a cationic terminated alcohol,an ester derived from a carboxylate terminated alcohol, a derivativeformed from alkylation with a cationic terminated epoxide, a derivativeformed from alkylation with an anionic terminated epoxides, andcombinations thereof; wherein the charged monomer reduces the amount ofagglomeration or precipitation of paraffin, wax, and/or asphaltenecrystals in the crude oil, a lubricant, a refinery fluid, and/or fueloil.

In an alternative non-limiting embodiment of the method, the foulingcomponent may be or include, but is not limited to wax, paraffins,asphaltene, resins, and combinations thereof and the fluid is anoil-based wellbore fluid.

There is provided in another form, a fluid composition having anoil-based fluid produced through a wellbore and an additive. Theadditive may include, but is not limited to, a block copolymer having atleast two components. The first component may be a charged monomer ofthe kinds recited in paragraph [0007], and the second component may be along chain fatty alcohol acrylate monomer; wherein the charged monomerreduces the amount of agglomeration or precipitation of crystals of theat least one fouling component in the oil-based fluid.

In an alternative non-limiting embodiment of the fluid composition, thefluid may be an oil-based wellbore fluid and the fouling component maybe present in the fluid in amount ranging from 2.5 wt % to about 20 wt%.

DETAILED DESCRIPTION

It has been discovered that an additive having a block copolymer with acharged monomer may act as a pour point depressant and/or at leastpartially reduce the accumulation of at least one fouling componentwithin a fluid by contacting the fluid with the additive. The additivemay be circulated within the wellbore prior to production of the fluid,so that the additive may contact the fluid upon production of the fluidinto the wellbore. The additive may also be added directly to thehydrocarbon fluid in an amount that may at least partially reduce thefouling components therein from accumulating. ‘Accumulation’ is definedherein to mean agglomeration and/or precipitation of the foulingcomponents.

Utilizing block copolymerization may allow for better synthesis ofacrylate polymers with well defined blocks, and allows monomers ofvarying uses to be combined into a multi-use copolymer. Here, the blockcopolymer may have at least two components. The second component may actas a crystal modifier to reduce further growth of wax crystals and keepthe size of the wax crystals smaller than they might otherwise havebeen. However, smaller crystals may still remain within the fluid, andthese smaller crystals may agglomerate and/or precipitate to form largercrystal structures that may still cause an increased pour point and/orclogging of well equipment.

By including a charged monomer (hereinafter referred to as the ‘firstcomponent’) in the block copolymer, the smaller crystals may beprevented or blocked from agglomerating and/or precipitating within thefluid. A block copolymer having this type of functionality may preventwax crystals from clogging well equipment and allows for the pour pointof the fluid to remain stable, if not lower the pour point, compared towhat would otherwise occur if the additive comprising the blockcopolymer had not contacted the fluid. Thus the copolymer additivesherein are more accurately characterized as pour point stabilizersrather than pour point depressants. In a non-limiting embodiment, thefluid may be a hydrocarbon fluid, such as crude oil, a refinery fluid, alubricant, a fuel oil, and combinations thereof. ‘Refinery fluid’ isdefined herein to be a hydrocarbon fluid that is ready to be refined oris in the process of being refined.

“Reduce” is defined herein to mean that the additive may suppress,inhibit or prevent the amount of accumulation of the fouling componentswithin the fluid if there are actually any fouling components presentwithin the fluid. That is, it is not necessary for the foulingcomponents to be entirely prevented or diminished from accumulating forthe methods and compositions discussed herein to be consideredeffective, although complete prevention is a desirable goal.

The first component may be or include, but is not limited to a chargedmonomer, either a cationic monomer or an anionic monomer, such as butnot limited to, a cationic acrylate based monomer, an anionic acrylatebased monomer, a sulfonated styrene, a cationic styrene derivative, anester derived from a cationic terminated alcohol, an ester derived froma carboxylate terminated alcohol, a derivative formed from alkylationwith a cationic terminated epoxide, a derivative formed from alkylationwith an anionic terminated epoxide, and combinations thereof. Morespecific non-limiting examples of the cationic acrylate based monomermay be or include, but are not limited to,acryl-oxyethyltrimethylammonium chloride,methacryloxyethyltrimethylammonium chloride,acryloxypropyltrimethylammonium chloride,methacryloxypropyltri-methylammonium chloride, correspondingmethylsulfate or sulfate salts thereof, and combinations thereof. Morespecific non-limiting examples of the anionic acrylate based monomer maybe or include, but are not limited to salts of acrylic acid, methacrylicacid, carboxyethyl acrylate, and carboxyethyl methacrylate. The firstcomponent may have a carbon chain ranging from about 2 carbon atomsindependently to about 8 carbon atoms, alternatively from about 2 carbonatoms independently to about 6 carbon atoms in another non-limitingembodiment. As used herein with respect to a range, “independently”means that any lower threshold may be used together with any upperthreshold to give a suitable alternative range.

The second component may be or include, but is not limited to a longchain fatty alcohol acrylate monomer. Other non-limiting examples of thefatty alcohol acrylate monomer may be or include an octadecyl acrylate,a C₂₀ acrylate, a C₃₀ acrylate, and combinations thereof. The secondcomponent may have a carbon chain ranging from about 10 carbon atomsindependently to about 40 carbon atoms, alternatively from about 18carbon atoms independently to about 30 carbon atoms, or from about 18carbon atoms independently to about 25 carbon atoms in anothernon-limiting embodiment.

By definition, herein, the second component is different from the firstcomponent. Moreover, ‘first component’ and ‘second component’ are usedas generic identifiers for at least two of the components within theblock copolymer. These terms are not used to specify any type of orderor layout of the components within the block copolymer.

In one non-limiting embodiment, the amount of the first component withinthe block copolymer may range from about 1 wt % independently to about20 wt % of the total block copolymer, alternatively from about 2 wt %independently to about 10 wt %, or from about 2 wt % independently toabout 5 wt % in another non-limiting embodiment. The amount of thesecond component within the block copolymer may range from about 80 wt %independently to about 99 wt % of the total block copolymer,alternatively from about 90 wt % independently to about 98 wt %, or fromabout 92 wt % independently to about 95 wt % in another non-limitingembodiment.

The additive may optionally include an aromatic solvent, such as but notlimited to, benzene, toluene, xylene, or at least one distillate such asaromatic 100 in a non-limiting embodiment, and combinations thereof. Theamount of the block copolymer within the additive may range from about15 wt % independently to about 50 wt %, or alternatively from about 20wt % independently to about 40 wt %, or from about 20 wt % independentlyto about 30 wt % in another non-limiting embodiment.

The block copolymer may be prepared by a polymerization method, such asbut not limited to, the living free radical polymerization, which mayalso be referred to as “reversible-deactivation radical polymerization”,and/or “controlled radical polymerization”. This type of polymerizationmay mediate the polymerization via a reversible chain-transfer processand may have an active polymer chain end with a free radical. AtomTransfer Radical Polymerization (ATRP) and ReversibleAddition-Fragmentation Chain-Transfer Polymerization (RAFT) are twotypes of living free radical polymerization that may be relevant topreparing the type of block copolymers described.

Atom transfer radical polymerization (ATRP) is a means of forming acarbon-carbon bond through a transition metal catalyst. The transitionmetal catalyst may allow for a uniform polymer chain growth. There maybe or include several important components for producing Atom TransferRadical Polymerizations, such as but not limited to, a monomer, aninitiator, a catalyst, a solvent, a ligand and temperature. Here, theinitiator may be or include, but is not limited to, ethylbromoisobutyrate, methyl bromoisobutyrate, ethyl 2-bromopropionate,methyl 2-bromopropionate, 2-bromopropionitrile, and combinationsthereof. The catalyst may be or include, but is not limited to, zerovalent copper; copper (I) salts, such as halides, oxides, or acetates;copper (II) salts, such as halides, acetates; and combinations thereof.The catalyst may be or include, but is not limited to, copper, nickel,iron, ruthenium, cobalt, rhenium, rhodium, molybdenum and combinationsthereof. The ligands may include, but are not limited to, tetramethylethylene diamine, pentamethyl ethylene triamine, and hexamethyl ethylenetetramine. Typical solvents may include, but are not limited to,toluene; 1,4-dioxane; xylene; anisole; DMF; DMSO; water; methanol; ACN;chloroform; bulk monomer; and combinations thereof.

RAFT polymerization also uses a chain transfer agent in the form of athiocarbonylthio compound to afford control over the generated molecularweight and polydispersity during a free-radical polymerization. As withother controlled radical polymerization techniques, RAFT polymerizationsmay be performed with conditions to favor low polydispersity indices anda pre-chosen molecular weight. The components for a RAFT polymerizationmay be or include, but are not limited to, a radical source (e.g.thermochemical initiator or the interaction of gamma radiation with somereagent), monomer, a chain transfer agent, a solvent, and combinationsthereof. The radical source may be or include, but is not limited to,azo compounds such as Azobisisobutyronitrile (AIBN); peroxides such asbenzoyl peroxide, hydroperoxides such as t-butylhydroperoxide; andcombinations thereof. The chain transfer agent may be or include, but isnot limited to dithiobenzoates, trithiocarbonates, dithiocarbamates, andcombinations thereof. The solvent may be or include, but is not limitedto toluene, xylenes, or a distillate such as aromatic 100 in anon-limiting embodiment, and combinations thereof.

The additive may further include an additional component that may impartother properties to the additive or the fluid. For example, the additivemay include an additional component, such as but not limited to, a coldflow improver, a scale inhibitor, a corrosion inhibitor, a bactericide,and combinations thereof, so long as the ingredient does notde-stabilize or break the dispersion of the block copolymer within thefluid.

The additive may be added to the fluid by a method, such as but notlimited to, injecting and/or spraying the additive into the fluid,wellbore, and combinations thereof. The additive may contact the fluidin an effective amount to at least partially reduce the accumulation ofthe fouling components therein as compared to an otherwise identicalfluid absent the additive. Alternatively, the amount of the additivewithin the fluid may range from about 100 ppm independently to about10,000 ppm, or alternatively from about 200 ppm independently to about5,000 ppm, or from about 500 ppm independently to about 4,000 ppm inanother non-limiting embodiment.

The additive may be useful in crude oil, lubricants, refinery fluids,and/or fuel oils having a fouling component content ranging from about7.5 wt % independently to about 20 wt %, alternatively from about fromabout 2.5 wt % independently to about 7.5 wt %, or from about 0.5 wt %independently to about 2.5 wt % in another non-limiting embodiment. Theadditive may target fouling components in size ranging from about 6carbon atoms independently to about 200 carbon atoms, alternatively fromabout 10 carbon atoms independently to about 150 carbon atoms, or fromabout 18 carbon atoms independently to about 100 carbon atoms in anothernon-limiting embodiment. The additive may function within the fluid whenthe temperature of the fluid ranges from about −40 C independently toabout 50 C, alternatively from about −20 C independently to about 40C,or from about −10 C independently to about 35 C in another non-limitingembodiment.

The additive may also include a dispersant, which is typically one ormore surfactants (or co-surfactants), used for dispersing and/oremulsifying the additive into the fluid. The dispersant may improve theseparation of particles and may prevent settling or clumping of theadditive once it contacts and subsequently mixes with the fluid. Suchdispersants may be or include, but are not limited to ethoxylatedalcohols, alkyl phenols, and combinations thereof.

The resulting additive may include the dispersant and the blockcopolymer. For dispersions intended to be used to treathydrocarbon/water mixtures, the dispersion may have a density betweenthat of water and the fluid being treated to allow the additive tolocate at the interface between the water and the hydrocarbon within thefluid. For example, the density may be less than 1 gm/cm³ and greaterthan the hydrocarbon or hydrocarbon-derived fluid. In one non-limitingexample, if the liquid is crude oil, which has a density from about 0.75gm/cm³ to about 0.96 gm/cm³, the density of the dispersion should bebetween at least about 0.75 gm/cm³ and about 1 gm/cm³, depending on thedensity of the actual crude oil being treated, but more typically fromabout 0.85 gm/cm³ to about 1 gm/cm³, depending on the density of theparticular crude oil.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof, and has been described aseffective in providing methods for preventing an accumulation of atleast one fouling component within a fluid, such as but not limited to,wax, paraffins, asphaltene, resins, and combinations thereof within ahydrocarbon fluid. However, it will be evident that variousmodifications and changes can be made thereto without departing from thebroader spirit or scope of the invention as set forth in the appendedclaims. Accordingly, the specification is to be regarded in anillustrative rather than a restrictive sense. For example, specificfluids, fouling components, additive components, monomers, and blockcopolymers falling within the claimed parameters, but not specificallyidentified or tried in a particular composition or method, are expectedto be within the scope of this invention.

The present invention may suitably comprise, consist or consistessentially of the elements disclosed and may be practiced in theabsence of an element not disclosed. For instance, the method mayconsist of or consist essentially of a method of contacting a fluidhaving at least one fouling component with an additive in an effectiveamount for at least partially reducing an accumulation of the foulingcomponent(s) as compared to an otherwise identical fluid absent theadditive where the additive includes at least two components, such as acharged monomer, and a long chain fatty alcohol acrylate monomer.

There is additionally provided a fluid composition having an oil-basedfluid an additive where the includes at least two components, such as acharged monomer, and a long chain fatty alcohol acrylate monomer, andwhere the fluid composition has a reduced accumulation of at least onefouling component as compared to an otherwise identical fluidcomposition absent the additive.

The words “comprising” and “comprises” as used throughout the claims,are to be interpreted to mean “including but not limited to” and“includes but not limited to”, respectively.

What is claimed is:
 1. A method comprising: contacting an oil-basedfluid comprising a paraffin, wax, and/or an asphaltene selected from agroup consisting of crude oil, a lubricant, a refinery fluid, fuel oil,and combinations thereof with an additive in an effective amount for atleast partially reducing an accumulation of the paraffin, wax, and/orasphaltene as compared to an otherwise identical fluid absent theadditive; wherein the additive comprises a block copolymer comprising atleast a first component and a second component; wherein the firstcomponent is a charged monomer, and the second component is a long chainfatty alcohol acrylate monomer, wherein the charged monomer is selectedfrom the group consisting of a salt of acrylic acid, a salt ofmethacrylic acid, a salt of carboxyethyl acrylate, a salt ofcarboxyethyl methacrylate, a sulfonated styrene, a cationic styrenederivative, a derivative formed from alkylation with a cationicterminated epoxide, a derivative formed from alkylation with an anionicterminated epoxides, and combinations thereof; and wherein the blockcopolymer reduces the amount of agglomeration or precipitation ofparaffin, wax, and/or asphaltene crystals in the crude oil, a lubricant,a refinery fluid, and/or fuel oil.
 2. The method of claim 1, wherein theoil-based fluid is selected from the group consisting of a crude oil, arefinery fluid, a lubricant, a fuel oil, and combinations thereof. 3.The method of claim 1, wherein the additive comprises from about 15 wt %to about 50 wt % of the block copolymer.
 4. The method of claim 1,wherein the block copolymer comprises from about 1 wt % to about 20 wt %of the first component.
 5. The method of claim 1, wherein the effectiveamount of the additive ranges from about 100 ppm to about 10,000 ppmbased on the fluid.
 6. The method of claim 1, wherein the additivefurther comprises an aromatic solvent selected from the group consistingof benzene, toluene, xylene, a distillate, and combinations thereof. 7.A method comprising: contacting an oil-based wellbore fluid having atleast one fouling component with an additive in an effective amount forat least partially reducing an accumulation of the at least one foulingcomponent within the oil-based wellbore fluid as compared to anotherwise identical hydrocarbon fluid absent the additive; wherein theat least one fouling component is selected from the group consisting ofwax, paraffins, asphaltene, resins, and combinations thereof; whereinthe additive comprises a block copolymer comprising at least a firstcomponent and a second component; wherein the first component is acharged monomer selected from the group consisting of an anionicacrylate based monomer, a sulfonated styrene, a cationic styrenederivative, a derivative formed from alkylation with a cationicterminated epoxide, a derivative formed from alkylation with an anionicterminated epoxides, and combinations thereof; and wherein the blockcopolymer reduces the amount of agglomeration or precipitation ofcrystals of the at least one fouling component in the oil-based wellborefluid.
 8. The method of claim 7, wherein the additive comprises about 15wt % to about 50 wt % of the block copolymer.
 9. The method of claim 7,wherein the effective amount of the additive ranges from about 100 ppmto about 10,000 ppm based on the fluid.
 10. A fluid compositioncomprising: an oil-based fluid produced through a wellbore; at least onefouling component; an additive comprising a block copolymer having along chain fatty acid acrylate monomer and a charged monomer, whereinthe charged monomer is selected from the group consisting of a salt ofacrylic acid, a salt of methacrylic acid, a salt of carboxyethylacrylate, a salt of carboxyethyl methacrylate, a sulfonated styrene, acationic styrene derivative, a derivative formed from alkylation with acationic terminated epoxide, a derivative formed from alkylation with ananionic terminated epoxides, and combinations thereof; and wherein theblock copolymer reduces the amount of agglomeration or precipitation ofcrystals of the at least one fouling component in the oil-based fluid.11. The fluid composition of claim 10, wherein the block copolymercomprises from about 1 wt % to about 20 wt % of the charged monomer. 12.The fluid composition of claim 10, wherein the amount of the additivewithin the oil-based fluid ranges from about 100 ppm to about 10,000ppm.
 13. The fluid composition of claim 10, wherein the additive furthercomprises an aromatic solvent selected from the group consisting ofbenzene, toluene, xylene, a distillate, and combinations thereof. 14.The fluid composition of claim 10, wherein the oil-based fluid isselected from the group consisting of a crude oil, a refinery fluid, alubricant, a fuel oil, and combinations thereof.
 15. The fluidcomposition of claim 10, wherein the at least one fouling component isselected from the group consisting of paraffin, wax, asphaltene, resins,and combinations thereof.
 16. A fluid composition comprising: anoil-based wellbore fluid; at least one fouling component present in thefluid in amount ranging from 0.5 wt % to about 20 wt %; an additivecomprising a block copolymer having a long chain fatty acid acrylatemonomer and a charged monomer selected from the group consisting of ananionic acrylate based monomer, a sulfonated styrene, a cationic styrenederivative, a derivative formed from alkylation with a cationicterminated epoxide, a derivative formed from alkylation with an anionicterminated epoxides, and combinations thereof; and wherein the blockcopolymer reduces the amount of agglomeration or precipitation ofcrystals of the at least one fouling component in the oil-based wellborefluid.
 17. The fluid composition of claim 16, wherein the amount of theadditive within the oil-based fluid ranges from about 100 ppm to about10,000 ppm.